# Lintel load calculation, explained

> A lintel carries the wall and floor above an opening. Here is how to find its load, the triangular masonry-load idea, and a worked example for a door or window head.

**Category:** Load paths  
**Author:** Sam Rivera (Structural engineer · Educator)  
**Published:** 2026-05-28

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A [lintel](https://en.wikipedia.org/wiki/Lintel) carries the load over an opening: the wall above it plus any floor or roof bearing on that wall through the opening zone. The useful idea is that for masonry, only a triangle of wall above the opening usually loads the lintel, because the masonry arches over. You add any floor load landing in the loaded zone, and the lintel spans the total to the wall each side. StructLoads models a lintel as a short beam carrying this load.

## What a lintel carries

A lintel is the beam over a door or window head in a [load-bearing wall](https://en.wikipedia.org/wiki/Load-bearing_wall). It carries whatever bears on it: the wall masonry above the opening, and any floor or roof reaction that lands on the wall within the loaded zone. The [structural load](https://en.wikipedia.org/wiki/Structural_load) on the lintel is therefore the wall self-weight in that zone plus those floor contributions, and the lintel spans it to the masonry on each side of the opening.

## The triangular masonry load

Masonry above an opening tends to arch, so it does not all bear on the lintel.

| Wall over the opening | What loads the lintel |
| --- | --- |
| Tall masonry, arching develops | A triangle of wall, about 45 to 60 degrees |
| Short masonry, no arching | The full rectangle of wall |
| Floor bears in the load zone | Add the floor reaction |
| Concentrated load over opening | Add it as a point load |

For a tall masonry wall, only the triangle of wall up to the apex bears on the lintel; above the apex the masonry self-supports by arching. So a lintel under tall masonry carries less than the full wall above it, which is why the triangular assumption is common and economical. The conditions are codified: [CMHA's TEK 17-01D on masonry lintel design](https://www.cmha.org/resource/tek-17-01d/) allows arching only when a symmetrical 45 degree triangle can form with at least 8 inches of wall above its apex, end bearing of at least 4 inches, no control joints beside the opening, and enough masonry each side to resist the arch thrust.

## A worked example

Take a 1.2 metre wide window opening in a 215 mm masonry wall at 19 kN per cubic metre. The triangular load is a triangle of base 1.2 metres and height about 0.6 metres (for a 45 degree spread), so an area of about 0.36 square metres of wall elevation. Its weight is 0.36 times 0.215 times 19, which is about 1.5 kN, carried as a triangular load on the lintel. If a floor reaction of 8 kN per metre also bears on the wall within the loaded width, add 1.2 times 8, which is about 9.6 kN. The lintel spans the total to the masonry each side.

## Floor and roof loads over the opening

A lintel only carries a floor or roof if that load lands on the wall inside the zone that loads the lintel. A floor reaction bearing directly above the opening, within the triangle or rectangle, adds to the lintel load, often as a concentrated patch. A floor bearing on the wall well away from the opening bypasses the lintel and goes straight into the masonry. So part of reading the case is deciding what actually reaches the lintel, the same load-path thinking as in [how loads transfer from a slab to beams](/blogs/how-loads-transfer-from-a-slab-to-beams).

## From load to lintel reactions

Once you have the load, the lintel is a short beam: it spans the opening and delivers a reaction to the masonry on each side, splitting by statics as in [how to calculate beam reactions from a slab](/blogs/how-to-calculate-beam-reactions-from-a-slab). Those reactions become bearing loads on the masonry at the jambs, which carry on down through the wall in the [bearing wall load takedown](/blogs/bearing-wall-load-takedown).

## When to use the full rectangle instead

The triangular assumption needs arching to develop, which it does in tall masonry. It is not safe for a wide opening, a wall too short above the opening for an arch to form, a non-masonry wall, or a concentrated load landing directly over the opening. In those cases assume the full rectangle of wall plus the real concentrated loads, which is more conservative. A qualified engineer confirms which assumption applies.

## Key takeaways: lintel load

A lintel carries the wall and any floor above the opening that bears on it. For tall masonry, only a triangle of wall loads the lintel because the masonry arches; for short walls or wide openings, use the full rectangle. Add floor loads landing in the zone, then treat the lintel as a short beam. StructLoads models it as a beam carrying this load, as a preliminary figure a qualified engineer confirms.

## Quick answers

### How do you calculate the load on a lintel?
Find the wall above the opening that bears on the lintel, plus any floor or roof load landing on that wall, and treat the total as a load over the lintel span. For masonry, often only a triangle of wall above the opening is assumed to load the lintel, because the masonry arches over. The lintel then spans that load to the wall on each side.

### What is the triangular load on a lintel?
For a masonry wall, the masonry above an opening tends to arch, so only a triangle of wall, typically at about 45 to 60 degrees from the ends of the opening, is assumed to bear on the lintel. Above the apex of that triangle, the wall self-supports. The triangular wall weight, plus any floor load within the loaded zone, is what the lintel carries.

### Does a lintel carry the floor above it?
Only if a floor or roof bears on the wall within the zone that loads the lintel. If a floor reaction lands on the wall above the opening and inside the assumed load triangle or rectangle, it adds to the lintel load, often as a point or patch load. If the floor bears outside that zone, it bypasses the lintel into the wall.

### When is the simple triangular lintel load not enough?
It is not enough when the opening is wide, the wall is short above it so no arching develops, a concentrated load such as a beam or column lands directly over the opening, or the wall is not masonry. There you assume the full rectangle of wall and the real concentrated loads, which is more conservative, and a qualified engineer confirms.